[CommCoreModule] make sure backupID is URL-safe string

Summary:
[ENG-9728](https://linear.app/comm/issue/ENG-9728/update-backupid-to-be-b64-url-safe-string).

Not sure if we need any additional conversion, this should be enough.

Test Plan: Test uploading backup

Reviewers: varun, bartek

Reviewed By: varun

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D13894

native/cpp/CommonCpp/CryptoTools/Tools.cpp

@@ -29,5 +29,11 @@ std::string Tools::generateRandomHexString(size_t size) {
   return Tools::generateRandomString(size, hexSigns);
 }
 
+std::string Tools::generateRandomURLSafeString(size_t size) {
+  static std::string urlSafeSigns =
+      "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_";
+  return Tools::generateRandomString(size, urlSafeSigns);
+}
+
 } // namespace crypto
 } // namespace comm

native/cpp/CommonCpp/CryptoTools/Tools.h

@@ -36,6 +36,7 @@ class Tools {
 public:
   static std::string generateRandomString(size_t size);
   static std::string generateRandomHexString(size_t size);
+  static std::string generateRandomURLSafeString(size_t size);
 };
 
 } // namespace crypto

native/cpp/CommonCpp/NativeModules/CommCoreModule.cpp

@@ -2502,7 +2502,7 @@ jsi::Value CommCoreModule::createNewBackupInternal(
 
           std::string backupID;
           try {
-            backupID = crypto::Tools::generateRandomString(32);
+            backupID = crypto::Tools::generateRandomURLSafeString(32);
           } catch (const std::exception &e) {
             error = "Failed to generate backupID";
           }